Conventionally, a treatment device for an endoscope including treatment parts, such as forceps, at the distal end thereof is known. When tissue within a body cavity is treated using such a treatment device for an endoscope, due to reasons such as the orientation of a treatment part that protrudes into the body not being suitable for the location of the target tissue to be treated, adjustment of the orientation of the treatment part may be required. In a case where such adjustment is performed, it is important to rotate the treatment part so as to exactly follow the manipulation of an operator.
Usually, in a case where the above-described treatment part is rotated, the manipulating part on the hand side of the treatment device for an endoscope is rotated. Here, in a case of a treatment device that pushes in manipulation wires connected to a treatment part such as forceps via a manipulating part to open and close the treatment part, a compressive force is applied in the axial direction of a coiled sheath together with the opening and closing. In this case, a multi-wire coil sheath around which a number of element wires are wound tends to become compressed in an axial direction, whereas the rotation transmissibility thereof is high compared to a single-line coiled sheath around which one element wire is wound. A displacement between the plurality of element wires (displacement of wires) may occur by this compression. Therefore, the coiled sheath is compressed in the axial direction, and an axial force to be transmitted to the distal end portion reduced, so that satisfactory treatment cannot be performed. As a result, the procedure becomes complicated.
In order to solve this problem, a treatment device for an endoscope described in Japanese Unexamined Patent Application, First Publication No. 2008-212620 is suggested. In this treatment device for an endoscope, a first coiled sheath around which one element wire is spirally wound is inserted through a second coiled sheath around which a plurality of element wires are spirally wound in the same direction. The distal end of the second coiled sheath is fixed to a movable distal end portion for performing treatment, and the proximal end of the second coiled sheath is fixed to a manipulating part.
In this way, using two types of coiled sheaths of the first coiled sheath and the second coiled sheath ensures a balance between a resistance to compression and a torque transmissibility.